The present invention relates generally to engine starters and generators, and more particularly to sensorless engine starter/generators.
In order to effectively start an aerospace or similar engine, constant or almost constant torque may be necessary. In order for a starter/generator to deliver this constant or almost constant torque, rotor position and speed sensing and processing may be required. Conventionally, sensors connected to a control unit are used to process rotor position and rotor speed information to create constant or almost constant torque during a start mode. These sensors may be located at a distance from the control unit, requiring undesirable additional connections and additional wiring between the sensors of a starter/generator and a control unit.
Sensorless sensing and processing of rotor position and rotor speed is an advancement over starter/generators requiring sensors. U.S. Pat. No. 6,809,496 describes a position sensor emulator providing sensorless sensing and processing of rotor position. The method of the position sensor emulator is based on supplying field windings of a starter/generator with constant or variable frequency AC voltage. A signal conditioning board may be used to extract two quadrature components using bandpass filters. Additionally, the position sensor emulator may provide a rectifier that rectifies exciter voltage signals of the starter/generator and a second bandpass filter that may filter the rectified exciter voltage signals to generate reference signals (α,β). These two signals may be processed to extract a rotor position. As noted, this particular method may utilize bandpass filters. Further, this method utilizes fairly complex mathematical calculations.
As can be seen, there is a need for an aircraft engine starter/generator not requiring bandpass filters. Further, there is a need for an aircraft engine starter/generator not requiring complex mathematical calculations.